1. Field of the Invention
The technology disclosed in the specification relates to an electric vehicle having a motor for running. The “electric vehicle” in the specification includes both an electric vehicle having only a motor for running without having an engine and a hybrid vehicle having the motor for running as well as the engine.
2. Description of Related Art
Japanese Patent Application Publication No. 2007-318849 discloses an electric vehicle including a main battery, a main electric power supply wire connected with the main battery, an electric power control unit including a smoothing capacitor that a smooths the voltage of the main electric power supply wire, a switch that is between the main battery and the electric power control unit and that switches the main electric power supply wire between conduction and non-conduction, a sub battery having a lower voltage than the main battery, a sub electric power supply wire connected with the sub battery, and a DC-DC converter that connects the main electric power supply wire on the electric power control unit side relative to the switch and the sub electric power supply wire and that can perform an boost operation to boost the electric power from the sub electric power supply wire and to supply the electric power to the main electric power supply wire.
In the above electric vehicle, when the switch is switched from the non-conduction to the conduction, a high inrush current flows through the main electric power supply wire shortly after the switch is switched to the conduction, if the voltage of the main battery is different from the voltage of the smoothing capacitor of the electric power control unit. Hence, before the switch is switched from the non-conduction to the conduction, it is necessary to perform the pre-charge of the smoothing capacitor such that the voltage of the main battery coincides with the voltage of the smoothing capacitor. In the electric vehicle in JP 2007-318849 A, the DC-DC converter performs the boost operation before the switch is switched from the non-conduction to the conduction. Thereby, it is possible to perform the pre-charge of the smoothing capacitor by supplying the electric power from the sub battery. On this occasion, in the DC-DC converter, an internal inductor and transformer suppress a sudden change in output current, and therefore, a high inrush current does not flow through the smoothing capacitor.